The White House said on Tuesday that post-election protests in Iran had begun to change the country, hours after Tehran issued a new denial that the disputed polls were marred by fraud.
White House spokesman Robert Gibbs was asked whether protestors braving a government crackdown had achieved anything since beginning to demonstrate against President Mahmoud Ahmadinejad's disputed reelection.
"I think the world is watching. I think they have accomplished something. They've drawn attention to what's going on in Iran," Gibbs told NBC.
"I absolutely think we've seen the beginnings of change in Iran."
But Gibbs stuck firm to the White House's insistence that it would not interfere in the internal political tumult in Iran, when asked whether Obama would endorse the idea of an opposition-led general strike.
"We're not going to get involved in endorsing or not endorsing specific actions inside of Iran," Gibbs said.
"This is for Iranians to debate -- their next leadership. I think the president wants to ensure that he doesn't become a political football that the regime uses against anybody that seeks justice in Iran."
Obama was expected to face a flurry of questions later on Tuesday at a solo White House news conference on his carefully calibrated stance towards the Iranian uprising.
The president has called for the rights of peaceful protests to be respected, and called on the Iranian government to avoid unjust and violent actions towards its people.
But he has warned that given the tortured US history with Iran, any US "meddling" in the country's internal affairs would be counterproductive.
Earlier, Iran ruled out canceling the disputed presidential vote as the world voiced increasing alarm at the crackdown on demonstrators who are posing the most serious challenge to the Islamic regime in 30 years.